Dipole-dipole interactions of sulfone groups as a tool for self-assembly of a 2D Covalent Organic Framework derived from a non-linear diboronic acid

Abstract

The utility of the nonlinear diboronic acid 2 , obtained from 3,7-dibromodibenzo[ b , d ]thiophene 5,5-dioxide 1 , for the preparation of Covalent Organic Frameworks was investigated. Despite significant deviation of boronic groups in 2 from the colinear arrangement, a highly crystalline porous material DBSO-COF was obtained by dehydrative polycondensation with 2,3,6,7,10,11-hexahydroxytriphenylene (HHTP) using a solvothermal approach. Subsequent PXRD studies supported by periodic DFT modelling revealed the formation of the 2D honeycomb-type lattice with eclipsed stacking model. The antiparallel orientation of neighboured layers is strongly favoured owing to dipole-dipole and C – H⋯O interactions of sulfone moieties. This gives the net stabilization energy of 45 kJ mol −1 per single sulfone motif, being primarily responsible for the effective formation of the ordered network and strongly contributing to its thermodynamic stability. The morphology was analyzed by SEM which revealed that the material forms uniform in size ca. 40 × 150 nm rod-like nano-crystallites. The Grand Canonical Monte Carlo (GCMC) simulation performed on a single nanoparticle of DBSO-COF allowed to reproduce the experimental isotherm. It also showed that N 2 molecules are mostly located close to the C – H bonds, while they are repulsed by sulfone groups. Apart from increasing the scope of useful boronic linkers beyond centrosymmetric structures, it was demonstrated that the presence of guest molecules in a porous network should be taken into account in order to obtain a more accurate prediction of porosity parameters. A highly crystalline porous Covalent Organic Framework was obtained from the nonlinear diboronic acid derived from dibenzo[ b , d ]thiophene 5,5-dioxide. The structure is precisely controlled by strong dipole-dipole and C–H⋯O S interactions of sulfone groups. • Development of a highly crystalline COF derived from a non-linear diboronic acid. • Precise structure control by dipole-dipole and HB interactions of sulfone groups. • Classical and periodic DFT approach to quantify the interactions between layers. • GCMC simulation of N2 sorption performed for a single nanoparticle.